In the words of Robert Browning, “polymathy is a distinctive feature of Byzantine culture”
and moreover one “not unconnected with the predominant role played by rhetoric.”294 And indeed scholars have often labeled members of the Byzantine educated elite as polymaths (notably Photios, Michael Psellos, and Theodore Metochites among others), based on the range and variety of their scholarly pursuits and literary production. Thus, polymathy appears to be a label with self-evident and straightforward meaning, ascribed to those well versed in various or all disciplines of the trivium and quadrivium. The intersection of scientific knowledge and rhetoric, which the notion of polymathy indicates, however, is in my opinion far from self-explanatory and consequently, it is scrutinized in the present chapter.
The transposition and use of philosophical or scientific material in a letter raises questions related to the interaction between content and genre; for instance, in what ways did Gregoras modify the technical mathematical or astronomical discussions in order to meet the literary conventions of the epistolary genre? More importantly, the change of literary form, i.e. of the means of rendering the material, entails a difference in the intention(s) and purpose(s) of the text and possibly a different audience. As Gregory Akindynos reported, Gregoras’ astronomical letters were performed publicly in Thessaloniki; there is also evidence that they were circulating among the circles of pepaideumenoi in Constantinople and Cyprus. Therefore, it is necessary to examine the motivation behind Gregoras’ rhetorical strategy of incorporation of philosophical and scientific elements in letters. Did it aim at maintaining an intellectual discussion? Did it perform a didactic and/or polemical function? What role did it play in establishing connections and in accumulating social prestige and achieving social promotion (these
294 Robert Browning, “Byzantine Literature,” CR 30, no. 2. New Series (1980): 270–271.
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goals being not mutually exclusive)?
In addition, by comparing scientific letters and treatises, I aim to reconstruct the implicit epistemological paradigms underlying the main thematic concerns of Gregoras’
letters. Though notorious for his radical skepticism concerning the possibilities for human reason to achieve firm knowledge,295 Gregoras, nevertheless, studied mathematics and astronomy with remarkable zeal and seriousness which are also reflected in his letters.
Worth mentioning is a group of six astronomical letters (Letters 28, 40, 53, 83, 103, and 114) the immediate context of which is the astronomical controversy Gregoras was engaged in during the 1330s. Despite their polemical character, the letters implicitly deal with the question of how the natural world should be examined and, by extension, with the definition of science and scientific truth.
Letter 12 offers another example of reflection on the methodological aspects of the scientific work and the proper methods for conducting it. Letter 6, on the other hand, employs a detailed mathematical discussion about the way two square numbers are related, in order to demonstrate the principles of friendship. Thus, the main objective of the present chapter consists first, in analysis of the intertextual relations between Gregoras’
scientific letters and related scientific texts. Thus, my inquiry examines the “translation” of technical scientific material into a scientifically informed rhetorical discussion. Second, the present chapter provides a much needed comprehensive discussion of Nikephoros Gregoras’ mathematical and astronomical letters, in relation to his general philosophical, cosmological and epistemological position.
295 Bydén, “The Criticism of Aristotle in Nikephoros Gregoras’ Florentius”; Michele Trizio, “On the Byzantine Fortune of Eustratios of Nicaea’s Commentary on Books I and VI of the Nicomachean Ethics,” in The Many Faces of Byzantine Philosophy, ed. Katerina Ierodiakonou and Börje Bydén, Papers and Monographs from the Norwegian Institute at Athens 1 (Athens: The Norwegian Institute at Athens, 2012), 199–224; and Demetracopoulos, “Nikephoros Gregoras.”
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The Mathematical Sciences in Byzantium: An Overview
Before I proceed to the close reading and analysis of Gregoras’ scientific letters and related treatises, I shall make some general remarks with respect to their theoretical background, that is, the mathematical sciences in Byzantium,296 mathematics and astronomy in particular.297 There are four major points one ought to emphasize with respect to the history of science in Byzantium. First, the mathematical sciences were studied and practiced as theoretical rather than experimental sciences, whence the certainty and truthfulness of their results were derived. Other types of knowledge, such as medicine, pharmacology, and alchemy relied much more on experience, observation, and practice.
Second, scientific study and production grew out of the classical heritage of Greek science and aimed at its preservation, clarification and emendation.298 A case in point is the period
296 By ‘mathematical sciences’ I refer to the sciences of the quadrivium, the τετρακτὺς τῶν μαθημάτων or the four methods defined by Nikomachos of Gerasa, i.e. arithmetic, geometry, music and astronomy.
297 Two classical surveys of the history of Greek mathematics are Thomas Little Heath, A History of Greek Mathematics, 2 vols. (Oxford: Clarendon Press, 1921) and Paul Tannery, La géométrie grecque (Hildesheim: Georg Olms, 1988). See also J. L. Heiberg, Geschichte der Mathematik und Naturwissenschaften im Altertum, Handbuch der Altertumswissenschaft, 1. Abt., 5 Bd., 2 hälfte (Munich: C. H. Beck, 1960) which treats also Byzantine authors, including Gregoras, as well as, N. Stuloff, “Mathematik in Byzanz,” Algorismus 1 (1988): 39–62 and Bydén, Theodore Metochites’ Stoicheiosis Astronomike, 216-262. Similarly, comprehensive background information on the history of ancient astronomy can be found in Paul Tannery, Recherches sur l’histoire de l’astronomie ancienne (Hildesheim; New York: G. Olms, 1976), while Mercier offers a collection of informative articles dealing with medieval astronomy in Raymond Mercier, Studies on the Transmission of Medieval Mathematical Astronomy, Variorium Collected Studies Series (Burlington, VT: Ashgate, 2004). For general introduction to Byzantine mathematical sciences, see Tihon, “Numeracy and Science”; Tihon, “Les sciences exactes à Byzance,” 380–434;
Tihon, “Astrological Promenade in Byzantium in the Early Palaiologan Period,” 265–90; Anne Tihon,
“Certainty, Doubt, and Errors in Byzantine Astronomy,” Early Science and Medicine 7, no. 3 (2002): 292–93, as well as Nikolaides, Science and Eastern Orthodoxy. On the textual transmission and readership of Byzantine mathematical texts, see Pérez Martín, “Al calor del texto antiguo.” On late Byzantine astronomy and astrology, see Pingree, “Gregory Chioniades and Palaeologan Astronomy,” 133–60; Pingree, “The Astrological School of John Abramius,” 189–215; Pingree, “Some Fourteenth-Century Byzantine Astronomical Texts,” 103–8, and Magdalino, L’orthodoxie des astrologues. Finally, an integrated perspective regarding the developments in science and philosophy in Byzantium, during the Palaiologan period in particular, is offered by Mergiali, L’enseignement et les lettres pendant l’époque des paléologues and by Michel Cacouros and Marie-Hélène Congourdeau, Philosophie et sciences à Byzance de 1204 à 1453: les textes, les doctrines et leur transmission: actes de la table ronde organisée au XXe Congrès international d’études Byzantines, Paris, 2001 (Peeters Publishers, 2006).
298 See Pérez Martín, “Al calor del texto antiguo,” 57; Anne Tihon, “Les sciences exactes à Byzance,” 381.
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after 1204, famously characterized by the increased production of compilations of scientific works whose chief purpose was the preservation of ancient knowledge on the subject, as well as the renewal of its circulation. It is in this period of proliferation of collections and compilations that a codification of a “canon of authorities” took place: Nikomachos of Gerasa (fl. ca. 100) together with Diophantos of Alexandria (fl. ca. 250) became the main reference for those interested in arithmetic, Euclid (fl. ca. 300 BCE) for the study of geometry, Heron of Alexandria (the first century CE) and Ptolemy (fl. ca. 130–175) for music and astronomy.299 It is noteworthy that the period after 1261 until the fall of Constantinople in 1453 is the period most saturated with scientific production during the Byzantine millennium.300 Third, one has to bear in mind the lack of institutionalization and support on behalf of the Byzantine imperial government for the study and practice of the higher mathematical sciences. This was not the case with medicine, for instance, since the Byzantine emperors invested in the creation and maintenance of medical schools and hospitals. The fourth main feature characterizing Byzantine science in particular, as well as Byzantine learned culture in general, consists in the lack of specialization on behalf of the scholars.301 Higher education in Byzantium was not university-based and did not follow an established curriculum.302 Thus, those educated Byzantines, who dedicated themselves to mathematics, typically left their contributions also in the fields of music, astronomy, and philosophy.303
Byzantine epistemic discourse inherited both the premise expressed at the beginning of Aristotle’s Metaphysics – namely, “[a]ll men by nature desire to know”304 – and its association with a number of classical Greek concepts related to the acquisition of
299 Pérez Martín, “Al calor del texto antiguo,” 62.
300 Tihon, “Les sciences exactes à Byzance,” 383.
301 Pérez Martín, “Al calor del texto antiguo,” 57.
302 See also Constantinides, Higher Education in Byzantium in the Thirteenth and Early Fourteenth Centuries (1204 - ca.
1310).
303 Pérez Martín, “Al calor del texto antiguo,” 57.
304 Aristotle, Metaphysics, I, 1, 980a21.
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knowledge and denoting desire for learning, philosophical pursuit of wisdom, and erudition or, reversely, inquisitiveness, meddlesomeness, and nosiness, e.g. πολυμάθεια, φιλομάθεια, and πολυϊστορ α; or πολυπραγμοσύνη, φιλοπραγμοσύνη, and περιεργ α. While the strife after knowledge was considered accordant to human nature, its intensification and excessiveness, and their respective ethical implications introduced additional epistemic discourses such as the determination of licit and illicit fields of study, as well as of useful and useless types of inquiry.305 Thus, the two most commonly used terms that express Byzantine attitude towards learning, be it properly scientific (e.g., mathematics, harmonics, and astronomy), or quasi-scientific (e.g., astrology, magic, and dream interpretation), namely φιλομάθεια and πολυμάθεια, denote multiple meanings: from the positive zeal for learning (φιλομάθεια) to the sometimes objectionable and unhealthy curiosity (πολυμάθεια is generally meant positively, but on occasion it can be synonymous with περιεργασ α and πολυπραγμοσύνη. Moreover, the latter can also be employed in its meaning of a pursuit of understanding). Though their meaning varies, they both indicate general and all-encompassing knowledge rather than specialized learning.306
Scientific works differed not only in terms of their topic, but also in terms of their literary style. There are, generally speaking, two major groups of scientific texts with respect to the register they were written in, namely those composed in classicizing Greek and those written in the vernacular.307 The first group usually deals with the so-called
‘noble’ matters, i.e. the advanced theoretical levels of the mathematical sciences. The second group includes practical and ‘reader-friendly’ manuals such as botanical lists, astrological prescriptions, and collections of arithmetical problems. The rough division of
305 Cf. Matthew Leigh, From Polypragmon to Curiosus: Ancient Concepts of Curious and Meddlesome Behaviour (Oxford:
Oxford University Press, 2013), 197.
306 John Duffy, “Reactions of Two Byzantine Intellectuals to the Theory and Practice of Magic: Michael Psellos and Michael Italikos,” in Byzantine Magic, ed. Henry Maguire (Washington, D.C: Dumbarton Oaks Research Library and Collection; Distributed by Harvard University Press, 1995), 91.
307 Tihon, “Les sciences exactes à Byzance,” 384.
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the Byzantine scientific texts according to style should be complemented by the addition of the category of translated works, e.g. from Arabic or Persian. Many times the Byzantine translations rendered the original word by word and in the case of foreign technical vocabulary, they preserved it in transliteration instead of providing an equivalent Greek term.
The mathematical sciences in Byzantium inherited their material and methods from the Greek mathematics of antiquity and were subsequently influenced by the developments in Arabic, Persian, Latin, and Jewish science. Mathematics was the foundation of astronomy, astrology, the computus (i.e. the calculation of the date of Easter), of financial transaction and architectural construction. Most influential in the studies of the mathematical sciences in Byzantium were the works of Euclid, Nikomachos of Gerasa, Diophantos of Alexandria, Apollonios of Perge (d. ca. 190 BCE), Archimedes (d. 212 BCE), Ptolemy, Pappos (fl. ca. 320), Theon of Alexandria (fl. ca. 360–380), and Heron. Nikomachos famously circumscribed the cycle of the four mathematical disciplines or tetraktys tōn mathēmatōn, namely arithmetic, geometry, music and astronomy.The works of Euclid, in turn, provided the basis for the study of geometry and were continuously read throughout the Byzantine millennium.
Evidence for Gregoras’ preoccupation with studying Euclid is the fact that he emended Book X of Euclid’s Elements by inserting an additional mathematical problem concerning the construction of a parallelogram.
The importance of Euclidean mathematics in Byzantium is comparable only to the influence Ptolemaic astronomy exerted on its medieval Greek counterpart. The systematic exposition of mathematical astronomy in Ptolemy’s Almagest and Handy Tables, as well as Theon’s commentaries were read continuously in Byzantium, and though during the thirteenth century the study of the higher mathematical sciences was interrupted for about a hundred years, astronomy was revitalized and reintroduced towards the end of this
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period.308
Gregoras’ astronomical activity, as well as the literary production stemming out of it, were an intrinsic part of one out of two trends characteristic for the development of astronomical studies during the Palaiologan period. On the one hand, Ptolemaic astronomy was consciously reintroduced in practice and publicized by several generations of scholars, most of them connected to the Chora monastery in Constantinople. The main driving force behind this enterprise was Theodore Metochites (d. 1332), though his work was already prepared by the efforts of Manuel Bryennios (fl. ca. 1300), Maximos Planoudes (ca. 1255–ca.
1305)309 and George Pachymeres (1242–ca. 1310). Nikephoros Gregoras continued Metochites’ efforts and then handed over the task to his own students, notably to Isaac Argyros (d. ca. 1375).310 On the other hand, an alternative trend in the study and practice of astronomy emerged under the influence of Islamic astronomical works coming mainly from Tabriz and introduced to Byzantium by Gregory Chioniades (d. ca. 1320) and later on popularized by scholars such as George Chrysokokkes (fl. ca. 1335–1350), Theodore Meliteniotes (d. 1393), and John Abramios (fl. 1370–1390).311 Moreover, through the court of Hugh IV of Lusignan (r. 1324–1359) those who maintained connection with Cyprus, like Nikephoros Gregoras, had access also to Latin astronomical treatises.312
Importantly, the revival of Ptolemaic astronomy in Palaiologan Byzantium occurred in parallel with at least two other, to my mind, potentially significant events. First, it is in
308 In Anne Tihon’s words, Ptolemaic astronomy in Palaiologan Byzantium appeared much more alive than it had been in late antique Alexandria. See Tihon, “Enseignement scientifique à Byzance,”107.
309 Planoudes made an autograph copy (Edinburgh, Advocates’ Library 18.7.15) of Cleomedes and Aratus. See Wilson, Scholars, 232.
310 PLP 1285. On Argyros’ activity, see also Mondrain, “Traces et mémoire,” 1–25; Mondrain, “Les écritures dans les manuscrits byzantins du XIVe siècle. Quelques problématiques,” 157–96; Bianconi, “La controversia palamitica. Figure, libri, testi e mani,” 337–76; Inmaculada Pérez Martín, “El ‘estilo Hodegos’ y su proyección en las escrituras constantinopolitanas,” SeT 6 (2008): 389–458; Estangüi Gómez, “Saint-Sauveur de Chôra. Un monastère catholique à Constantinople dans le troisième quart du XIVe siècle,” 140–97.
311 Paul Magdalino, “The Byzantine Reception of Classical Astrology,” in Literacy, Education and Manuscript Transmission in Byzantium and beyond, ed. Catherine Holmes, Judith Waring (Leiden: Brill, 2002): 33-57.
312 David Pingree, “The Byzantine Version of the ‘Toledan Tables’: The Work of George Lapithes?,” DOP 30 (1976): 85–132.
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the late thirteenth-early fourteenth century that one of the seminal Latin medieval cosmological texts was translated into Greek by Maximos Planoudes, namely Macrobius’
commentary on Cicero’s Somnium Scipionis.313 In her critical edition of Planoudes’
translation of Cicero’s Somnium Scipionis, Annamaria Pavano listed seven fourteenth-century manuscripts transmitting the translation in question: Vat. gr. 116, 1r-4r and 57r-61r;
Par. suppl. gr. 1101, ff. 71r-75v; Par. gr. 1000, ff. 268r-274r; Marc. gr. Z 508 (the fourteenth–
fifteenth centuries), ff. 1r-7r; Monac. gr. 439 (the fourteenth–fifteenth centuries), ff. 59r-74v;
Monac. gr. 495 (the fourteenth–fifteenth centuries), ff. 204v-210v; Vat. gr. 115 (the fourteenth or fifteenth centuries), ff. 1r-10r.314 Three of them render also Planoudes’ translation of Macrobius’ commentary: Vat. gr. 116, Marc. gr. Z 508, and Vat. gr. 115. Vat. gr. 116, as it was discussed earlier, is Gregoras’ autograph and contains predominantly his writings. Thus, Gregoras was familiar with Planoudes’ translations and, as Sbordone has shown, he further appropriated them in his short arithmological treatise dedicated to the number seven.
Secondly, it ought to be mentioned that the Palaiologan Ptolemaic revival, regarding astronomy, closely followed the translation of Ptolemy’s Almagest into Latin, first from Greek in 1160 and then, from Arabic by Gerard of Cremona around 1175. Thus, the Ptolemaic planetary system of eccentrics and epicycles came to the fore of Latin astronomy only in the thirteenth century,315 that is, less than a century before it was revisited in Byzantium. Thus, it is worth exploring to what extent the Palaiologan revival of Ptolemy
313 See Wilson, Scholars, 230. Planoudes translated also Cicero’s Somnium Scipionis. On translations of philosophical texts from Latin to Greek in the thirteenth century, see Börje Bydén, “‘Strangle Them with These Meshes of Syllogisms!’: Latin Philosophy in Greek Translations of the Thirteenth Century,” in Interaction and Isolation in Late Byzantine Culture: Papers Read at a Colloquium Held at the Swedish Research Institute in Istanbul, 1-5 December, 1999, ed. Jan Olof Rosenqvist, Swedish Research Institute in Istanbul Transactions 13 (Stockholm, London, New York: Swedish Research Institute in Istanbul, 2004), 133–57. Modern critical editions of Planoudes’ translations of both texts are available. See M. Tullii Ciceronis Somnium Scipionis in graecum translatum, ed. Pavano and Μάξιμου Πλανούδη (1255-1305) του υπομνηματος εις τον “Ονειρον του Σκηπίωνος,” ed.
Megas.
314 M. Tullii Ciceronis Somnium Scipionis in graecum translatum, xii-xiv.
315 Gabriela Ilnitchi, “‘Musica Mundana,’ Aristotelian Natural Philosophy and Ptolemaic Astronomy,” Early Music History 21 (2002): 50-51.
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was motivated by the parallel developments in the west.316
Finally, one also ought to bear in mind that the increased interest in Ptolemaic astronomy during the Palaiologan period happened simultaneously to the rediscovery of Ptolemy’s Geography in the end of the thirteenth century.317 The driving force behind the revival of Ptolemaic geography in Palaiologan Byzantium was, once again, the activity of Maximos Planoudes who in 1295 successfully acquired and reedited Ptolemy’s treatise.
Worth mentioning are two codices containing the Geography: 1) Vat. gr. 177, dated to the end of the thirteenth century, which was in Planoudes’ possession while he was residing at the monastery of Christ Saviour in Chora; 2) and Vat. gr. 191, a thirteenth or fourteenth-century manuscript containing in addition a number of astronomical works. Both manuscripts do not include any maps; however, they both contain notes indicating that the codices were supposed to comprise twenty-six or twenty-seven maps respectively. The three oldest manuscript witnesses of Ptolemy’s Geography containing maps date to the late thirteenth century and are also associated with Planoudes’ editorial activity, namely codd. Urbinas gr.
82 with twenty-seven maps, Seragliensis 57, and Fragmentum Fabricianum Graecum. In sum, Maximos Planoudes was actively engaged not only in reestablishing the mathematical sciences in Byzantium, but he was also behind the restored interest in Ptolemy, not only as an authority on astronomy, but also as a supreme example of geography and cartography.
Finally, Planoudes actively translated Latin texts into Greek, and, although his translations of Augustine’s On the Trinity and Boethius’ The Consolation of Philosophy are considered of larger significance, for the purposes of the present study, most important is his rendition of Cicero’s Somnium Scipionis and Macrobius’ relevant commentary.318 Planoudes’ scholarly
316 For some remarks on the subject, see Bydén, “‘Strangle Them with These Meshes of Syllogisms!’,” 135-137.
317 Dilke, “Cartography in the Byzantine Empire,” 258–275.
318 On Planoudes’ translation of Cicero’s Somnium Scipionis, see Wolfgang O. Schmitt, “Lateinische Literatur in Byzanz. Die Übersetzungen des Maximos Planudes und die moderne Forschung,” Jahrbuch der österreichischen byzantinischen Gesellschaft 17 (1968): 127–48; Annamaria Pavano, “Caratteri stilistici della traduzione planudea del Somnium Scipionis,” Sileno 14 (1988): 157–69; Elisabeth Fisher, “Planoudes, Holobolos, and the Motivation for Translation,” GRBS 43 (2002): 77–104.
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projects are significant not only because part of his library remained at Chora and consequently was available to Metochites and Gregoras, but also because the results of his work on astronomy in combination with his translations of Cicero and Macrobius may have influenced later Byzantine cosmological theories.
Chapter 1: The Hortatory Letter concerning Astronomy
In order to study the configurations of the fixed stars, the movements and conjunctions of the five planets, the positions of the two luminaries, the sun and the moon, with respect to the earth and to each other, one would use an astrolabe, an astronomical instrument known probably since the second century CE319 which converted with the help of stereographical projection the three-dimensional celestial sphere visible from a defined geographical latitude into a dynamic two-dimensional map of the sky projected on the equatorial plane.
Though only one Byzantine astrolabe survives today,320 there are descriptions of the instrument, depictions, as well as treatises and diagrams dedicated to its construction and usage preserved in numerous Byzantine codices.321 One such description, a favorite among
319 Otto Neugebauer, “The Early History of the Astrolabe. Studies in Ancient Astronomy IX,” Isis 40, 3 (1949):
240.
320 Nikolaides, Science and Eastern Orthodoxy, 88: “In effect, the only Byzantine instruments that have been conserved to our day are an astrolabe of Persian inspiration, constructed in 1062, and fragments of another astrolabe.”
321 The treatise on the astrolabe composed by John Philoponos (d. ca. 570), as well as the earlier description of the instrument by Synesios (d. ca. 413), served as models for Palaiologan contributions on the subject such as Nikephoros Gregoras’ On the Construction of the Astrolabe (in two redactions), as well as the works by Isaak Argyros and Theodore Meliteniotes. The actual observational use of astronomical instruments in Byzantium is also attested. One such instance is contained in a lengthy marginal note on f. 275r in codex Laurentianus 28, 16, authored probably in 1389 in Constantinople, by the astronomer and astrologer John Abramios. John mentioned that with the help of a diopter, he observed one of the fixed stars, namely the Southern Crown, and calculated its longitude. Then, he reported adjusting his astrolabe accordingly and calculating the time of night when his observation was recorded. The estimation of the precise hour was confirmed by the sound of a clock. Gregoras also made use of the astrolabe. As Ševčenko pointed out, Gregoras inserted a correction in the margin of f. 159v of Vat. gr. 165 in which he suggested a different value regarding the spring equinox of March 17, according to what he had determined with the help of an astrolabe. See Ševčenko, Études, 117, note 2.
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scholars discussing shadow projection with respect to Byzantine art, comes from the works of Nikephoros Gregoras:
The delineation of a sphere on a flat plane is similar to painting. For just as the painters seek to imitate objects exactly, not according to their true properties, but [...] so as to make them visually more plausible, so, too, the geometricians and astronomers delineate on a flat plane solid objects, such as octahedrons and cubes and all spherical bodies, like stars, the heavens, and the earth.322
The excerpt comes from the second redaction of Gregoras’ treatise on the construction of the astrolabe, published by Delatte in 1939.323 For his edition Delatte used one fifteenth-century manuscript, namely Baroccianus 166 (ff. 230r-236v) which contained also the first redaction of Gregoras’ treatise. The second redaction, however, is preserved also in a fourteenth-century manuscript, namely Vat. gr. 1087 (ff. 312v-320v), which was unknown to Delatte at the time. Codex Vat. gr. 1087 has gained considerable attention recently mostly due to the fact that it is one of the very few illuminated Byzantine astronomical manuscripts.324 For the purposes of the present study, the Vaticanus is important, since it is also an example of Nikephoros Gregoras’ editorial practice. The miscellaneous astronomical codex was assembled during the first half of the fourteenth century and Gregoras, assisted
322 Cyril Mango, ed. and transl., Art of the Byzantine Empire: Sources and Documents, Englewood Cliffs, 1972, 254. Gregoras, Astrolabica B, line 19-29: ζωγραφ α γάρ τ ς ἐστιν ἡ ἐν ἐπιπέδῳ τῆς σφα ρας καταγραφ · ὥσπερ οὖν οἱ ζωγράφοι τὴν μὲν μ μησιν ἀκριβῆ τῶν πραγμάτων ἐπε γονται οὐ καθ’ ὅσον πεφύκασιν ἔχοντα, ἀλλ’
ὅσον ἐπιγινώσκειν τοὺς βλέποντας κατὰ τὸ ἐφικτὸν ἀνθρωπ νῃ φύσει καὶ νῦν μὲν τὰ τῶν ὑψιστεγῶν οἰκιῶν μ κη, νῦν δὲ τὰ πλάτη δεικνύουσι συστελλόμενά πως καὶ πρὸς ἑαυτὰ συνιζάνοντα κατά τε τὸ χρειῶδες τῆς τέχνης καὶ ἅμα τῆς ἐς ὄψιν πιθανωτέρας συγκαταθέσεως, οὕτω καὶ γεωμέτραι καὶ ἀστρονόμοι τὴν τῶν στερεῶν ἐν ἐπιπέδῳ ποιοῦνται καταγραφ ν, ὀκτάεδρά φημι καὶ κύβους, ἀστέρας τε καὶ οὐρανὸν καὶ γῆν καὶ πάντα ὅσα τῶν σωμάτων σφαιρικά.
323 Gregoras, “Astrolabica B.”
324 See for instance Fabio Giudetti and Anna Santoni, eds., Antiche stelle a Bisanzio: Il codice Vaticano greco 1087, Seminari e convegni, 32 (Pisa: Edizioni della Normale, 2013), a monograph that resulted from a conference organized by the Illuminated Astronomical Manuscripts research group at the Scuola Normale Superiore in Pisa in February 2012 and dedicated to this same manuscript.